Mockito Matcher for a TypeReference

Question

I am trying to write a Java unit test using Mockito but am having trouble to get a matcher to work.

I want to test the following class

CustomService.java

public class CustomService {

private final ApplicationProperties props;

public CustomService(ApplicationProperties props){
    this.props = props;
}

private final ObjectMapper mapper = new ObjectMapper();
public void method(JsonNode message) throws CustomException {
    try {
        List<String> actions = mapper.readValue(message.get("actions").toString(), mapper.getTypeFactory().constructCollectionType(List.class, String.class));
        System.out.println(actions);
    } catch (IOException ex){
        throw new CustomException(ex);
    }
}
}

I have a CustomException class

CustomExcepton.java

@ResponseStatus(value = HttpStatus.INTERNAL_SERVER_ERROR)
public class CustomException extends Exception {

public CustomException(Throwable cause) {
    super(cause);
    }

}

I want to test that the CustomException is thrown. I am using Mockito. I have tried the below but the given statement doesn't seem to pick up the (readValue) line of code in the method

CustomServiceTest.java

public class CustomServiceTest {

private final ApplicationProperties props = mock(ApplicationProperties.class);
private final CustomService customService = new CustomService(props);
private static final ObjectMapper objectMapper = new ObjectMapper();

@Test
public void CustomExceptionIsThrown() throws Exception {
    ObjectMapper mapper = mock(ObjectMapper.class);
    given(mapper.readValue(anyString(), any(TypeReference.class))).willThrow(new IOException("This is a test"));
    String json = "{\"actions\":[\"ac1\",\"ac2\",\"ac3\",\"ac4\"]}";
    JsonNode d = objectMapper.readTree(json);
    assertThrows(CustomException.class, () ->
            customService.method(d));
    }
}

I get the following error when I run the test

Expected exception.CustomException to be thrown, but nothing was thrown..

Help would be appreciated.

Answer 1

I also met this same problem, and i find that although i mock objectMapper like " when(objectMapper.readValue(anyString(), any(TypeReference.class))).thenReturn(xxxx);" but when i invoke the test, the first param of readValue(xx,xx) is null which should be a String object. So, you might want to check readValue method input param again.Hope it will help.